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On the universal trends in the noise reduction due to wavy leading edges in aerofoil–vortex interaction

Published online by Cambridge University Press:  17 May 2019

Jacob M. Turner  and
Jae Wook Kim Open the ORCID record for Jae Wook Kim [Opens in a new window]
Jacob M. Turner
Affiliation:
Aerodynamics and Flight Mechanics Research Group, University of Southampton, SouthamptonSO17 1BJ, UK
Jae Wook Kim*
Affiliation:
Aerodynamics and Flight Mechanics Research Group, University of Southampton, SouthamptonSO17 1BJ, UK
*
†Email address for correspondence: [email protected]
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Abstract

Existing studies suggest that wavy leading edges (WLEs) offer substantial reduction of broadband noise generated by an aerofoil undergoing upstream vortical disturbances. In this context, there are two universal trends in the frequency spectra of the noise reduction which have been observed and reported to date: (i) no significant reduction at low frequencies followed by (ii) a rapid growth of the noise reduction that persists in the medium-to-high frequency range. These trends are known to be insensitive to the aerofoil type and flow condition used. This paper aims to provide comprehensive understandings as to how these universal trends are formed and what the major drivers are. The current work is based on very-high-resolution numerical simulations of a semi-infinite flat-plate aerofoil impinged by a prescribed divergence-free vortex in an inviscid base flow at zero incidence angle, continued from recent work by the authors (Turner & Kim, J. Fluid Mech., vol. 811, 2017, pp. 582–611). One of the most significant findings in the current work is that the noise source distribution on the aerofoil surface becomes entirely two-dimensional (highly non-uniform in the spanwise direction as well as streamwise) at high frequencies when the WLE is involved. Also, the sources downstream of the LE make crucial contributions to creating the universal trends across all frequencies. These findings contradict the conventional LE-focused one-dimensional source analysis that has widely been accepted for all frequencies. The current study suggests that the universal trends in the noise-reduction spectra can be properly understood by taking the downstream source contributions into account, in terms of both magnitude and phase variations. After including the downstream sources, it is shown in this paper that the first universal trend is due to the conservation of total (surface integrated) source energy at low frequencies. The surface-integrated source magnitude that decreases faster with the WLE correlates very well with the noise-reduction spectrum at medium frequencies. In the meantime, the high-frequency noise reduction is driven almost entirely by destructive phase interference that increases rapidly and consistently with frequency, explaining the second universal trend.

JFM classification

Acoustics: Aeroacoustics Acoustics: Hydrodynamic noise Acoustics: Noise control
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 871 , 25 July 2019 , pp. 186 - 211
Copyright
© 2019 Cambridge University Press 

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References

Agrawal, B. R. & Sharma, A. 2016 Numerical analysis of aerodynamic noise mitigation via leading edge serrations for a rod-airfoil configuration. Intl J. Aeroacoust. 25 (8), 734–756.10.1177/1475472X16672322Google Scholar
Amiet, R. K. 1975 Acoustic radiation from an airfoil in a turbulent stream. J. Sound Vib. 41, 407–420.Google Scholar
Ayton, L. J. & Kim, J. W. 2018 An analytic solution of the noise generated by gust-aerofoil interaction for plates with serrated leading edges. J. Fluid Mech. 853, 515–536.Google Scholar
Biedermann, T. M., Chong, T. P., Kameier, F. & Paschereit, C. O. 2017 Statistical-empirical modeling of airfoil noise subjected to leading-edge serrations. AIAA J. 55 (9), 3128–3142.10.2514/1.J055633Google Scholar
Blandeau, V. P., Joseph, P. F., Jenkins, G. & Powles, C. J. 2011 Comparison of sound power radiation from isolated airfoils and cascades in turbulent flow. J. Acoust. Soc. Am. 129 (6), 3521–3530.10.1121/1.3569706Google Scholar
Chaitanya, P., Joseph, P., Narayanan, S., Vanderwel, C., Turner, J., Kim, J. W. & Ganapathisubramani, B. 2017 Performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence-aerofoil interaction noise. J. Fluid Mech. 818, 435–464.Google Scholar
Chong, T. P., Vathylakis, A., McEwen, A., Kemsley, F., Muhammad, C. & Siddiqi, S.2015 Aeroacoustic and aerodynamic performances of an aerofoil subjected to sinusoidal leading edges. In 21st AIAA/CEAS Aeroacoustics Conference. AIAA Paper 2015-2200.10.2514/6.2015-2200Google Scholar
Clair, V., Polacsek, C., Le Garrec, T., Reboul, G., Gruber, M. & Joseph, P. 2013 Experimental and numerical investigation of turbulence-airfoil noise reduction using wavy edges. AIAA J. 51 (11), 2695–2713.10.2514/1.J052394Google Scholar
Ffowcs Williams, J. E. & Hawkings, D. L. 1969 Sound generation by turbulence and surface in arbitrary motion. Phil. Trans. R. Soc. Lond. A 264, 321–342.Google Scholar
Goldstein, M. E. 1976 Aeroacoustics. McGraw-Hill.Google Scholar
Hansen, K., Kelso, R. & Doolan, C. 2012 Reduction of flow induced airfoil tonal noise using leading edge sinusoidal modifications. Acoust. Australia 40 (3), 172–177.Google Scholar
Juknevicius, A. & Chong, T. P. 2018 On the leading edge noise and aerodynamics of thin aerofoil subjected to the straight and curved serrations. J. Sound Vib. 425, 324–343.Google Scholar
Kim, J. W. 2007 Optimised boundary compact finite difference schemes for computational aeroacoustics. J. Comput. Phys. 225, 995–1019.Google Scholar
Kim, J. W. 2010 High-order compact filters with variable cut-off wavenumber and stable boundary treatment. Comput. Fluids 39, 1168–1182.10.1016/j.compfluid.2010.02.007Google Scholar
Kim, J. W. 2013 Quasi-disjoint pentadiagonal matrix systems for the parallelization of compact finite-difference schemes and filters. J. Comput. Phys. 241, 168–194.10.1016/j.jcp.2013.01.046Google Scholar
Kim, J. W. & Haeri, S. 2015 An advanced synthetic eddy method for the computation of aerofoil-turbulence interaction noise. J. Comput. Phys. 287, 1–17.Google Scholar
Kim, J. W., Haeri, S. & Joseph, P. 2016 On the reduction of aerofoil-turbulence interaction noise associated with wavy leading edges. J. Fluid Mech. 792, 526–552.10.1017/jfm.2016.95Google Scholar
Kim, J. W., Lau, A. S. H. & Sandham, N. D. 2010a CAA boundary conditions for airfoil noise due to high-frequency gusts. Proc. Eng. 6, 244–253.10.1016/j.proeng.2010.09.026Google Scholar
Kim, J. W., Lau, A. S. H. & Sandham, N. D. 2010b Proposed boundary conditions for gust-airfoil interaction noise. AIAA J. 48 (11), 2705–2709.Google Scholar
Kim, J. W. & Lee, D. J. 2000 Generalized characteristic boundary conditions for computational aeroacoustics. AIAA J. 38 (11), 2040–2049.10.2514/2.891Google Scholar
Kim, J. W. & Lee, D. J. 2004 Generalized characteristic boundary conditions for computational aeroacoustics, part 2. AIAA J. 42 (1), 47–55.Google Scholar
Kim, J. W. & Morris, P. J. 2002 Computation of subsonic inviscid flow past a cone using high-order schemes. AIAA J. 40 (10), 1961–1968.Google Scholar
Lau, A. S. H., Haeri, S. & Kim, J. W. 2013 The effect of wavy leading edges on aerofoil-gust interaction noise. J. Sound Vib. 332, 6234–6253.Google Scholar
Lyu, B. & Azarpeyvand, M. 2017 On the noise prediction for serrated leading edges. J. Fluid Mech. 826, 205–234.10.1017/jfm.2017.429Google Scholar
Mathews, J. & Peake, N. 2018 An analytically-based method for predicting the noise generated by the interaction between turbulence and a serrated leading edge. J. Sound Vib. 422, 506–525.Google Scholar
Narayanan, S., Chaitanya, P., Haeri, S., Joseph, P., Kim, J. W. & Polacsek, C. 2015 Airfoil noise reductions through leading edge serrations. Phys. Fluids 27, 025109.Google Scholar
Roger, M. & Moreau, S. 2016 Airfoil turbulence-impingement noise reduction by porosity or wavy leading-edge cut: experimental investigations. In Proceedings collection: INTER-NOISE and NOISE-CON Congress and Conference Proceedings, pp. 6366–6375. Institute of Noise Control Engineering.Google Scholar
Tong, F., Qiao, W., Xu, K., Wang, L., Chen, W. & Wang, X. 2018 On the study of wavy leading-edge vanes to achieve low fan interaction noise. J. Sound Vib. 419, 200–226.Google Scholar
Turner, J. M. & Kim, J. W. 2017 Aeroacoustic source mechanisms of a wavy leading edge undergoing vortical disturbances. J. Fluid Mech. 811, 582–611.Google Scholar
Turner, J. M. & Kim, J. W. 2019 Secondary noise sources in a vortical flow interacting with an undulated leading edge. J. Fluid Mech. (submitted).Google Scholar
Yee, H. C., Sandham, N. D. & Djomehri, M. J. 1999 Low-dissipative high-order shock-capturing methods using characteristic-based filters. J. Comput. Phys. 150, 199–238.10.1006/jcph.1998.6177Google Scholar